X-ray energy analyzer

ABSTRACT

An energy dispersive X-ray analyzer comprising an evacuable enclosure which includes X-ray generating means and X-ray detecting means, the enclosure having movably mounted therein sample selecting means and X-radiation selecting means, each of which are operatively connected to respective external control means.

United States Patent [191 Kirkendall et al.

[ Nov. 18, 1975 X-RAY ENERGY ANALYZER [75] Inventors: Thomas D. Kirkendall, Potomac,

Md.; Howard D. Doolittle, Stamford, Conn.

[73] Assignee: The Machlett Laboratories,

' Stamford, Conn.

22 Filed: Apr. 8, 1974 21 Appl. No.: 458,944

[56] References Cited UNITED STATES PATENTS 2,046,714 7/1936 Wilson et al 250/226 2,995,973 8/1961 Barnes et a]. 250/505 X 3,248,543 4/1966 Pitchford 250/279 3,336,494 8/1967 Nagashima et a]. 250/272 3,391,276 7/1968 Delarue 250/274 Primary Examiner-James W. Lawrence Assistant Examiner-T. N. Grigsby Attorney, Agent, or FirmHarold A. Murphy; Joseph D. Pannone; John T. Meaney [57] 1 ABSTRACT An energy dispersive X-ray analyzer comprising an evacuable enclosure which includes X-ray generating means and X-ray detecting means, the enclosure having movably mounted therein sample selecting means and X-radiation selecting means, each of which are operatively connected to respective external control means.

16 Claims, 4 Drawing Figures HIGH VOLTAGE I POWER I SUPPLY 48 Q 7 5 I62 24 /a 54 m5: l6 7 I ES. PUMP /4 I j A52 5 I /58 j Patent Nov. 18, 1975 Sheet10f2 3,920,984

UD L TAGE 42 Eg 5 IIIIIIII II/IIIII |x|o COUNTS f.s.

US. Patent Nov. 18,1975 Sheet 2 of2 3,920,984

CIRCUIT PULSE DETECTOR AMPLIFIER HEIGHT ANALYZER 58 '1 RECORDER POWER SUPPLY 3 CARBON /78 OXYGEN FLUORINE PHOTON ENERGY IN eV SODIUM BACKGROUND OF THE INVENTION Y This invention relates generally to X-ray spectro scopy and is concerned more particularly with energy dispersive X-ray spectroscopy apparatus having improved excitation and detection efficiency for-analyzing low atomic number elements.

In an energy dispersive X-ray analysi'ssystem,'the primary source of X-radia'tion may comprise an X-ray tube of the conventional type which emits a continuous, or white, band "of X-radiation. This -ty'pe of X- radiation may be employed, for example, in irradiating a sample of multielement material to cause theirradiated elements'therein to emit, simultaneously; respective characteristics lines of X-radiation-which have as sociated energy valuesindicative' of the emitting ele ments. The fluorescence X-rays, thus produced,'may be detected by conventional rneans,such as a proportional counter, for example, inac cor'dance'with their associated energy values; The resulting train of output pulses may be separated electronically, as a'pulse height analyzer, for example, in accdrdance with the associated energy values to produce a'h output energy spectrum, whereby the emitting elements in the sample may be identified. l

Each element may-be identified by its principal char acteristic wavelength, which is emfmee most strongly when the exciting X-radiation is 'r'estrictedsubstantially to'wavelengths slightly shorter'than the corresponding absorption edge wavelength. Consequently, the energy dispersive X-ray analysis system maybeprovided' with a secondary X-ray source which supplies X-radiation of the required wavelengths for'selectively exciting a spe' cific element in the sample to'obtain a strong. emission of its characteristic X rays econd'ary xsource may comprise,for example, a bodybfs'ele'cted materialwhich is irradiated acontinuousband of K radiation emanating from an X raytube fAs ares'ult, the selected material ierriits' characteristic line radiation which includes X-rays having one or more de sired wavelengths for selectively exeiting the speci fi'c'f element in the sample. Accordingly, when the fluorescence X-"radiation is incident on thesample, the s'pe cific element emits strong characteristic line X- radiation, thereby disclosing presence of the element in the sample. l

Thus, thetechnique of energydispersive Xgray analysis is especially suited for the detection and ,identifi cation of one or moreele m'entsina sample of material.

However, difficultiesareencountered when this te ch-.

nique is used for'th e analysis of light elements, for ,e x

amplef Wh en irradiatedjthese lighaelements emit characteristic X-rays of, relativel y long wavelengths and correspondingly low'energies. As aresult, alarg e percent-i age of the characteristic X-rays emitted by the light elements may be absorbed by. air molecules, before reaching the detector. V'acuiim means may betemployedfor vide energy dispersive X-ray analyzer apparatus having means forimproving X-ray detectionsensitiyity, partica I, ularlyfor the analysis of the light elements, andmeans for readily changing components of the apparatus when desired.

SUMMARY OF THE INVENTION Accordingly, this invention provides an energy dispersive X=ray analyzer apparatus including an evacuable enclosure comprised of a housing having operatively connected thereto X-ray generating means and X-ray detecting means, such that each is readily accessible for servicing or replacement. The housing may be provided with an opening through which suitably coupled pumping means may evacuate the enclosure. Movably mounted within the enclosure are respective sample selecting means and X-radiation selecting means which are accessible through suitable ports in the housing for changing components thereof when desired. The sample selecting means and the X-radiation selecting means are connected to respective external control means whichmay be operated independently of one another. I

The sample selecting means includes a movable sample. holder'having means for supporting a plurality of sample materials, one of which may be moved into atest position within the enclosure by the associated external control means. The sample selecting means may comprise a turntable carrying a plurality of samples-and mounted on a rotatable shaft which extends hermetically out of the enclosure to the external control means.

The X-radiation selecting means comprises a movable X-ray limiting device holder having means for supporting a plurality of X-ray limiting devices, such as collimators, filters, fluorescers, and combinations thereof,.for example, each of which may be moved into suitable alignment with a sample in the test position by the associated external control means. The X-radiation selecting means may comprise a disc provided with a plurality of openings wherein respective X-ray limiting devices are disposed, and mounted on a rotatable shaft which extends hermetically out of the enclosure to the associated control means. An arcuate portion of the disc is suitably aligned with the test position, and by rotating the support shaft successive arcuate portions of the disc may be brought into alignment with the test position..

.The X-ray'generating means may comprise one or more sources of primary X-rays, such as an X-ray tube of the conventional type, for example. The anode target of the X-ray tube may be made of any suitable material such as rhodium, for example, which will provide a desired band of X-radiation. Alternatively, the anode target may be made of a plurality of materials, each of which provides desired X-ray wavelengths.

One source of primary X-rays is disposed to direct a beam of X-radiation through an X-ray limiting device, such as a filter, for example, of the X-ray selecting means and onto the samplein the test position. A plurality ofprimary X-ray sources may be suitably disposed for directing respective beams of X-radiation onto otherbeam limiting devices, such as fluorescers, for example, of the X-ray selecting means thereby producing fluorescence type characteristic line X- radiation for selectively irradiating elements in the test sample. t

The X-ray detecting means may comprise a conventional type of X-ray detector, such as a gas-flow proportional counter, for example, and also may include electronic means suitably connected to the X-ray detector for analyzing the output thereof.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of this invention, the following more detailed description makes reference to the accompanying drawing wherein:

FIG. I is a schematic view of an energy dispersive X-ray analyzer apparatus which embodies the invention;

FIG. 2 is a plan view of a radiation selecting means taken along line 2-2 in FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a block diagrammatic view of suitable electronic means for use with the apparatus shown in FIG. I; and

FIG. 4 is a graph of a typical energy spectrum obtainable in the practice of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawing wherein like characters of reference designate like parts, there is shown in FIG. 1 an energy dispersive X-ray analyzer apparatus including an evacuable enclosure comprised of a housing 12, which may be made of aluminum, for example. The housing 12 comprises a base 14 hermetically attached to upright opposing side walls 16 and opposing end walls 18 (only one of which is shown in FIG. 1). Extending hermetically through the base 12, as by means of O-ring 20, for example, is a rotatable shaft 24 which may be made of aluminum, for example. The shaft 24 terminates at its outer end in a control knob 26, and is rotatably supported in a bearing 28 which is affixed to the inner surface of base 14. Adjacent the bearing 28, the shaft 24 is provided with an indexing means, such as detent mechanism 30, for example, which lightly locks the rotatable shaft 24 in predetermined angular positions.

The inner end of shaft 24 is fixedly secured, as by keying, for example, to a turntable 32 which may be made of aluminum, for example. The upper surface of turntable 32 is provided with a circular array of spaced recesses 34 which receive therein respective samples 36 of material for energy dispersive X-ray analysis. By manipulating external control knob 26, the shaft 24 and turntable 32 may be rotated to carry respective samples 36 sequentially to a test position, designated generally as 38. Also, the locking positions of detent mechanism 30 may be designed to coincide with respective recesses 30 being located in the test position. Thus turntable 32, rotatable shaft 24, detent mechanism 30, and control knob 26 constitute a sample selecting means 22 for moving a particular sample 36 to a test position 38 for irradiation.

The upright walls 16 and 18 of housing 12 are hermetically attached to a pairof sloping walls, 40 and 42, respectively, which converge to meet in an heremetically sealed, apex joint 44 extending the length of housing 12 and approximately over test position 38. A portion of the sloped wall 40 adjacent turntable 32 is provided with a port 46 which may be opened for changing the component samples 36 on the turntable and then resealed hermetically, as by means of O-ring 48, for example. At least a portion of the port 46 may conveniently be made of transparent material, such as leaded glass for example, whereby the angular position of turntable 32 may be observed while manipulating the control knob 26. The angular position of turntable 32 also may be indicated externally of housing 12 by any convenient means, such as a pointer attached to shaft 24, for example.

Adjacent the apex joint 44, the sloped wall is provided with a shouldered opening 50 which is aligned with the test position 38. Suitably disposed in the shouldered opening 50 is a flanged open end of a collimating tube 52, which is made of rigid material, such as copper, for example. The tube 52 extends into housing 12 in line-of-sight arrangement with the test position 38. An O-ring 54 may be seated on the flanged end of tube 52 such that an X-ray detecting means 56 may be hermetically mounted over the opening 50 to constitute a part of the evacuable enclosure 10. The X-ray detecting means 56 may comprise a conventional type of X-ray detector 58, such as a gas flow proportional counter. for example, having an entrance window 59 which is aligned with the collimating tube 52.

On the other side of apex joint 44 and adjacent thereto, the sloping wall 42 is provided with a shouldered opening 60 which is aligned with the test position 38. An O-ring 62 may be peripherally seated in the shouldered opening 60 and compressed by an annular flanged portion 64 of a first source 66 of primary X- 'rays. Accordingly, the first source 66 is hermetically mounted in opening 60 to form a part of the evacuable enclosure 10. The first source 66 is disposed to direct a beam 68 of X-radiation onto a sample 36 in the test position 38, thereby causing the test sample 36 to emit characteristic line X-radiation which may be detected by the X-ray detecting means 56. Thus, the sloped walls 40 and 42 provide means for supporting respectively, the X-ray detecting means 56 and the first source 66 of primary X-rays approximately over the test position 38.

' Furthermore, by locating the apex joint 44 in close spaced relationship with the test position 38, the X-ray paths from the first source 66 to test sample 36 and from the latter to detecting means 56 may be minimized. In this manner, optimum X-ray excitation and detection efficiency may be achieved for analyzing light elements, such as the elements having lower atomic members than aluminum, for examples.

The first source 66 of primary X-rays may comprise an X-ray tube 70 of the convention type having a sealed envelope 72 provided with an X-ray window 74. The tube 70 is disposed such that a beam 68 of X-radiation passing through the window 74 is directed toward a sample 36 in the test position 38. X-ray tube 70 includes a filamentary cathode 76 disposed to direct a beam of emitted electrons onto a spaced anode target 78, which is made of a suitable material, such as rhodium, for example. Alternatively, anode target 78 may include arcuate portions 78a and 78b, respectively, each of which is comprised of a suitable material, such as rhodium and chromium, respectively, and is rotatable into operative alignment with the cathode 76 and the window 74.

The cathode 76 is suitable connected, as by respective conductors 80 and 82, for example, to a filament power supply 83 which provides current for heating the cathode 76 to an electron emitting temperature. The anode target 78 and the cathode 76 are connected, as by respective conductors 84 and 86, for example, through a switching means 88 to a high voltage source 90. When the switching means 88 is actuated to connect the high voltage source 90 between the anode target 78 and the cathode 76, a beam of emitted electrons impinges on the anode target 76 with sufficient energy to produce the beam 68 of primary X-rays. Preferably, the voltage applied between the cathode 76 and the anode target 78 is sufficiently high to excite K characteristic line X-radiation from the target material. Consequently, the beam 68 of X-radiation emanating from window 74 of X-ray tube 70 generally comprises a continuous band of X-radiation, called Bremsstrahlung, and may also include characteristic line X-radiation, of the anode target material.

Extending hermetically through the sloped wall 42 of housing 12, as by means of O-ring 92, for example, is a rotatable shaft 94 which may be made of aluminum, for example. The shaft 94 terminates at its outer end in a control knob 96 and is rotatably supported in a bearing 98 which is affixed to the inner surface of the sloped wall 42. Adjacent the bearing 98, the shaft 94 is provided with an indexing means, such as detent mechanism 100, for example. Fixedly secured to the inner end of shaft 94, as by keying, for example, is a radiation limiting device holder comprising an apertured disc 102 which may be made of aluminum, for example. Adjacent its periphery, the disc 102 is provided with a circular array of shouldered openings 106, each of whichreceives therein a respective radiation limiting device 108.

An arcuate portion of disc 102 and a corresponding portion of the circular array is interposed, in spaced relationship, between the first source 66 of primary X- rays and a sample 36 in test position 38. By manipulating control knob 96, the shaft 94 and disc 102 may be rotated to carry the respective radiation limiting devices 108 sequentially into aligned interposed relationship with the first source 66 and the test position 38. Also, the locking positions of detent mechanism 100 may be designed to coincide with respective openings 106 of the circular array being located in alignment with the first source 66 and a sample 36 in the test posi-' tion 38.

Adjacent the connecting side wall 16, a portion of the A sloped wall 42 is provided with a port 110 which may be opened for the purpose of changing radiation limiting devices 108 and then resealed hermetically, as by means of O-ring 112, for example. At least a portion of the port 110 may be conveniently made of transparent material, such as leaded glass for example, whereby the angular position of the disc 102 may be observed while manipulating the control knob 96. The angular position of disc 102 may be indicated externally of the housing 12 by any convenient means, such as a pointer suitably attached to the shaft 94, for example.

As shown more clearly in FIG. 2, the disc 102 may be provided with a plurality of openings 106, such as openings 106a-106f, for examples, which receive therein respective radiation limiting devices 108a-108f. The radiation limiting device 108a may comprise a cylindrical plug 114 of X-ray absorbing material, such as lead, for example, having centrally disposed therein a through aperture 116. Thus, the device 108a may serve as a collimator for reducing the diamet- .ric size of a high intensity X-ray beam 68 such that only a corresponding small area of the test sample 36 is irradiated. In this mannerfthe resulting characteristic line X-radiation emitted by elements in the test sample 36 may be maintained below the saturation level of the X-ray detecting means 56.

The radiation limiting device 1081), on the other hand, may comprise a cylindrical plug 118 of X-ray absorbing material, such as lead, for example, having centrally disposed therein a through aperture 120 of larger diameter than the aperture 114 in radiation limiting device 108a. The device 108b may serve as a collimator for permitting a larger diametric portion of a relatively low intensity X-ray beam 68 to irradiate a correspondingly larger area of the test sample 36. As a result, the elements in test sample 36 are excited more efficiently thereby increasing the detection sensitivity of the X-ray detecting means 56, particularly for light elements.

The radiation limiting device 108C may comprise a hollow sleeve 122 made of suitable material, such as lead, for example, which is closed at an end thereof adjacent the first source 66 by a thin sheet 124 of low energy X-ray fluorescent material, such as aluminum, for example. Preferably, the sheet 124 is provided with an optimum thickness for enhancing the principal characteristic X-rays emitted by the material of sheet 124, and for absorbing lower energy X-rays from the beam 68. Thus, the radiation limiting device 1080 may serve as an X-ray filter for removing from the beam 68 soft" X-rays having less energy than the characteristic line X-radiation produced by exciting the material of sheet 124. Accordingly, the resulting X-radiation emanating from the end of device 1080 adjacent test sample 36 comprises fluorescent characteristic X-radiation generated in sheet 124, and Bremsstrahlung or white X- radiation having sufficient energy to pass through sheet 124.

Similarly, radiation limiting device 108d may comprise a hollow sleeve 126 made of suitable material, such as lead, for example, which is closed at an end adjacent the first source 66 by a thin sheet 128 of higher atomic number material, such as titanium, for example, than the sheet 124 of device 108(. Preferably, the sheet 128 is provided with an optimum thickness for enhancing the higher energy characteristic X-rays emitted by the material of sheet..128, and for absorbing a higher corresponding number of lower energy X-rays from the beam 68 than the sheet 124. Thus, the radiation limiting device 108d may serve as an X-ray filter for removing from the beam 68 X-rays having more energy than the X-rays absorbed by sheet 124 but having less energy than the characteristic line X-radiation emitted by sheet 128. Accordingly, the resulting X-radiation emanating from the end of device 108d adjacent the test sample 36 comprises fluorescent characteristic X- radiation generated in sheet 128 and Bremsstrahlung or white radiation having a higher average energy than the Bremsstrahlung X-radiation transmitted through sheet 124 of beam limiting device 1086.

The Bremsstrahlung or white X-radiation such as transmitted through the respective devices 1086' and 108d, for examples, may be minimized by employing plug-type fluorescers, such as used in radiation limiting devices 1082 and l08f, for examples. The radiation limiting devices 108a and l08f may comprise respective cylindrical plugs 130 and 132 of low energy X-ray fluorescent materials, such as chromium and titanium, respectively, for examples, which efficiently excite light elements. As a result, the light elements in test sample 36 emit respective characteristic line X-radiation which may be detected by the X-ray detecting means 56. Preferably, the respective radiation limiting devices 108e and 108f are advantageously irradiated by a second source 136 which is suitably located for directing a beam 144 of primary X-rays onto the respective surfaces of fluorescers 130 and 132 adjacent the test position 38.

Referring to FIG. 1, a portion of the base 14 opposite the disc 102 may be provided with a shouldered opening 138 having peripherally seated therein an O-ring 140. The second source 136 of primary X-rays may carry a flanged portion 142 which compresses the O- ring 140, thus providing means for hermetically attaching second source 136 to housing 12 as a part of the evacuable enclosure 10. The second source 136 is disposed to direct an X-ray beam 144 onto an adjacent surface of a radiation limiting device 108 which. is located over the test position 38. Accordingly, a radiation limiting device of the fluorescer type, such as 108e, for example, may be rotated into position over the test sample 36 where the adjacent surface of device 108e is irradiated by the beam 144 of primary X-rays. The resulting low energy fluorescence X-rays emanating from the irradiated surface of device 108e impinge on the closely spaced surface of testsample 36. In this manner, any light elements in the test sample 36 may be efficiently excited to emit characteristic X-rays which may be of sufficient intensity to be detected by the X-ray detecting means 56.

Thus it may be seen that the disc 102 carrying radiation limiting devices 108, the rotatable shaft 94, detent mechanism 100, and external control knob 96 constitute a radiation selecting means 134 for disposing a radiation limiting device 108 in operative alignment with the test sample 36 and a source of primary X-rays whereby a desired band of X-radiation is obtained for irradiating the test sample.

The second source 136 of primary X-rays may comprise an X-ray tube 146 of the conventional type having a sealed envelope 148 provided with an X-ray transparent window 150. The window 150 is disposed in envelope 148' such that X-rays exiting from the tube 146 through the window 150 form the beam 144 which is directed toward a device 108 located over the test position 38. The Xray tube 146 includes a filamentary cathode 152 connected externally to a filament power supply 154 and disposed within envelope 148 to direct a beam of emitted electrons onto an anode target 156 which is made of suitable material, such as rhodium, for example. The cathode 152 and anode target 156 are connected as by respective conductors 158 and 160, for example, through the switching means 88 to the high voltage source 90. Accordingly, the switching means 88 may be actuated to disconnect the high voltage source 90 from the first source 66 and connect it to the second source 136 when a radiation limiting device of the fluorescer type,such as 108e and 108 for examples, is rotated into position over the test sample 36.

Although only two sources of primary X-rays are shown and described, it will be readily apparent to those skilled in the art that a greater number of such sources may be provided, if so desired. Thus, it may be seen that the apparatus of this invention includes an X-ray generating means which may comprise one or more sources of primary X-rays, each hermetically attached to housing 12 as a part of enclosure and disposed to direct a respective beam of primary Xrays into the enclosure.

Approximately percent of the K characteristic X radiation emitted by titanium, for example, which has an atomic number of 22, is absorbed, at atmospheric pressure in an air path length of about thirteen nches Accordingly, the equivalent air paths are much shorter for the correspondingly lower energy K characteristic wavelengths emitted by light elements which have atomic number less than thirteen, Therefore, in order to increase the excitation efficiency of low energy fluorescers, such as titanium, for example, and to improve the detection sensitivity of X-ray detecting means 56, particularly when light elements are being analyzed, the apparatus of this invention is provided with means for evacuating the enclosure 10. Consequently, a portion of the enclosure 10, such as a side wall 16 of housing 12, for example, may be provided with a suitable opening 162 for coupling the enclosure to an exhaust means, such as a control valve 164 and a connecting pump 166 of the rotary type, for example. In addition, the apparatus of this invention provides a radiation selecting means 134 which rotates a low energy fluorescer material, such as titanium, for example, into position over the test sample 36, and provides a second source of primary X-rays for irradiating the surface of the fluorescer adjacent the test sample 36. Also, the apparatus of this invention provides a housing 12 having a sloped wall 40 which supports the X-ray detecting means 56 approximately over the test sample 36 and in close spaced relationship therewith.

The X-ray detector 58 may comprise a gas-flow proportional counter of the conventional type, such as Model D2825 made by LND of Oceanside, N.Y., for example, which produces a train of output pulses, each pulse having a height corresponding to the ionization energy of an incident X-ray. As shown in FIG. 3, the detector 58 may be connected to a suitable power supply 168, such as Model No. 3002 made by Canberra Industries of Meriden, Conn., for example. The train of output pulses produced by detector 58 may be fed through a conventional amplifier 170 such as Model 1718 made by Canberra Industries of Meriden, Conn., for example, to the input of a multichannel pulse height analyzer 172, such as Model 8100 also made by Canberra Industries of Meriden, Conn., for example. The pulse height analyzer 172 electronically sorts and counts the pulses according to height and produces an output energy spectrum 178 which may be shown visually by a suitably connected display means, such as a conventional type display tube 174 or a stylus type recorder 176, for examples.

A typical output energy spectrum 178 is shown in FIG. 4 and includes energy peaks 179, 180, 181 and 182 which indicate the presence of light elements: carbon, oxygen, fluorine, and sodium, respectively. The detection of fine traces of carbon, which has an atomic number of 6, illustrates the excitation efficiency and detection sensitivity obtainable in the practice of this invention.

From the foregoing, it will be apparent that all of the objectives of this invention have been achieved by the structures shown and described. It will be also apparent however, that various changes may be made by those skilled in the art without departing from the spirit of the invention as expressed in the appended claims. lt is to be understood, therefore, that all matter shown and described is to be interpreted as illustrative and .not in a limiting sense. A

We claim: Y 1

1. An energy dispersive X-ray analyzer apparatus including;

an evacuable enclosure-comprising a hollow housing having means forhermetically attaching X-raygenerating means and X-ray detecting means thereto as demountable parts of the enclosure;

sample selecting means comprising a sample holder having means for supporting a plurality of samples within the housing, and means for moving a selected portion of the sample holder into a test position within the enclosure; and

X-radiation selecting means comprising a device holder having means for supporting a plurality of radiation limiting devices including fluorescer devices within the housing, and means for moving a particular portion of the device holder into operative alignment with the test position.

2. An energy dispersive X-ray analyzer apparatus as set forth in claim 1 wherein the sample holder includes a portion thereof disposed in the test position, and the associated moving means includes control means for moving successive portions of the sample holder into the test position.

3. An energy dispersive X-ray analyzer apparatus as set forth in claim 2 wherein the control means includes indexing means for regulating movement of successive portions of the sample holder into the test position.

4. An energy dispersive X-ray analyzer apparatus as set forth in claim 2 wherein the control means include adjustment means disposed externally of the housing for initiating and stopping movement of successive portions of the sample holder into the test position.

5. An energy dispersive X-ray analyzer apparatus as set forth in claim 1 wherein the device holder includes a portion thereof disposed in operative alignment with the test position, and the associated moving means includes control means for moving successive portions of the device holder into operative alignment with the test position.

6. An energy dispersive X-ray analyzer apparatus as set forth in claim 5 wherein the control means includes indexing means for regulating movement of successive portions of the device holder into operative alignment with the test position.

7. An energy dispersive X-ray analyzer apparatus as set forth in claim 5 wherein the control means includes adjustment means disposed externally of the housing for initiating and stopping movement of successive portions of the device holder into operative alignment with the test position.

8. An energy dispersive X-ray analyzer apparatus including:

an evacuable enclosure comprising a hollow housing having a plurality of hermetically sealable openings in the walls thereof;

a sample selecting means comprising means for supporting a plurality of samples within the housing and means for moving a selected sample into a test position within the enclosure;

X-radiation selecting means comprising means for supporting a plurality of radiation limiting devices including fluorescer devices within the housing and means for moving a particular radiation limiting device imdep'ermm alignment with the selected sarnple; H I X-ray generating means hermetically mounted on the housing as-a defining part-oftheenclosure and disposed to direct X-radiation toward. the particular radiation limiting device; and X-ray detecting means hermetically mounted on the housingas a definingpart of the enclosure and disposed to receive. X-radiation from the selected sample.

9. An energy dispersive X-ray analyzer apparatus as set forth in claim 8 wherein the housing includes port means for providing access to the sample selecting means and the radiation selecting means.

10. An energy dispersive X-ray analyzer apparatus as set forth in claim 8 wherein the sample selecting means comprises a shaft rotatably mounted in the housing and fixedly attached to a turntable having means for carrying thereon a plurality of samples and having an arcuate portion disposed in the test position.

11. An energy dispersive X-ray analyzer apparatus as set forth in claim 8 wherein the X-radiation selecting means comprises a shaft rotatably mounted in the housing and fixedly attached to an apertured disc having an arcuate portion thereof disposed in operative alignment with the test position.

12. An energy dispersive X-ray analyzer apparatus as set forth in claim 11 wherein the X-radiation selecting means includes external control means coupled to the shaft for rotating a selected arcuate portion of the disc into operative alignment with the test position.

13. An energy dispersive X-Ray analyzer apparatus as set forth in claim 12 wherein the selected arcuate portion is provided with aperture defining means for supporting a respective radiation limiting device in operative alignment with the selected sample in the test position.

14. An energy dispersive X-ray analyzer apparatus as set forth in claim 13 wherein the X-ray generating -means is positioned to direct a beam of X-radiation through the respective radiation limiting device and onto the selected sample.

15. An energy dispersive X-ray analyzer apparatus as set forth in claim 14 wherein the respective radiation limiting device is a fluorescer device and the X-ray generating means is positioned to direct a beam of X- radiation onto a portion of the fiuorescer device adjacent the selected sample.

16. An energy dispersive X-ray analyzer apparatus including:

an evacuable enclosure comprising a hollow housing having a convergent pair of sloped walls hermetically attached to one another in an apex joint located approximately over a test position within the housing;

a sample selecting me ans comprising turntable means for supporting with the housing a circular array of arcuately spaced samples, one being located in the test position, and means for rotating a selected sample of the array into the test position;

X-radiation selecting means comprising apertured disc means for supporting within the housing a circular array of arcuately spaced radiation limiting devices including fluorescer devices one being aligned with the test position, and means for rotating a selected radiation limiting device into alignment with the selected sample;

apex joint to receive X-rays emitted from the selected sample; and

second X-ray generating means hermetically mounted as a defining part of the enclosure or a wall opposite the first X-ray generating means and disposed to direct a beam of X-radiation onto a portion of the selected radiation limiting device adjacent the selected sample. 

1. An energy dispersive X-ray analyzer apparatus including; an evacuable enclosure comprising a hollow housing having means for hermetically attaching X-ray generating means and X-ray detecting means thereto as demountable parts of the enclosure; sample selecting means comprising a sample holder having means for supporting a plurality of samples within the housing, and means for moving a selected portion of the sample holder into a test position within the enclosure; and X-radiation selecting means comprising a device holder having means for supporting a plurality of radiation limiting devices including fluorescer devices within the housing, and means for moving a particular portion of the device holder into operative alignment with the test position.
 2. An energy dispersive X-ray analyzer apparatus as set forth in claim 1 wherein the sample holder includes a portion thereof disposed in the test position, and the associated moving means includes control means for moving successive portions of the sample holder into the test position.
 3. An energy dispersive X-ray analyzer apparatus as set forth in claim 2 wherein the control means includes indexing means for regulating movement of successive portions of the sample holder into the test position.
 4. An energy dispersive X-ray analyzer apparatus as set forth in claim 2 wherein the control means include adjustment means disposed externally of the housing for initiating and stopping movement of successive portions of the sample holder into the test position.
 5. An energy dispersive X-ray analyzer apparatus as set forth in claim 1 wherein the device holder includes a portion thereof disposed in operative alignment with the test position, and the associated moving means includes control means for moving successive portions of the device holder into operative alignment with the test position.
 6. An energy dispersive X-ray analyzer apparatus as set forth in claim 5 wherein the control means includes indexing means for regulating movement of successive portions of the device holder into operative alignment with the test position.
 7. An energy dispersive X-ray analyzer apparatus as set forth in claim 5 wherein the control means includes adjustment means disposed externally of the housing for initiating and stopping movement of successive portions of the device holder into operative alignment with the test position.
 8. An energy dispersive X-ray analyzer apparatus including: an evacuable enclosure comprising a hollow housing having a plurality of hermetically sealable openings in the walls thereof; a sample selecting means comprising means for supporting a plurality of samples within the housing and means for moving a selected sample into a test position within the enclosure; X-radiation selecting means comprising means for supporting a plurality of radiation limiting devices including fluorescer devices within the housing and means for moving a particular radiation limiting device into operative alignment with the selected sample; X-ray generating means hermetically mounted on the housing as a defining part of the enclosure and disposed to direct X-radiation toward the particular radiation limiting device; and X-ray detecting means hermetically mounted on the housing as a defining part of the enclosure and disposed to receive X-radiation from the selected sample.
 9. An energy dispersive X-ray analyzer apparatus as set forth in claim 8 wherein the housing includes port means for providing access to the sample selecting means and the radiation selecting means.
 10. An energy dispersive X-ray analyzer apparatus as set forth in claim 8 wherein the sample selecting means comprises a shaft rotatably mounted in the housing and fixedly attached to a turntable having means for carrying thereon a plurality of samples and having an arcuate portion disposed in the test position.
 11. An energy dispersive X-ray analyzer apparatus as set forth in claim 8 wherein the X-radiation selecting means comprises a shaft rotatably mounted in the housing and fixedly attached to an apertured disc having an arcuate portion thereof disposed in operative alignment with the test position.
 12. An energy dispersive X-ray analyzer apparatus as set forth in claim 11 wherein the X-radiation selecting means includes external control means coupled to the shaft for rotating a selected arcuate portion of the disc into operative alignment with the test position.
 13. An energy dispersive X-Ray analyzer apparatus as set forth in claim 12 wherein the selected arcuate portion is provided with aperture defining means for supporting a respective radiation limiting device in operative alignment with the selected sample in the test position.
 14. An energy dispersive X-ray analyzer apparatus as set forth in claim 13 wherein the X-ray generating means is positioned to direct a beam of X-radiation through the respective radiation limiting device and onto the selected sample.
 15. An energy dispersive X-ray analyzer apparatus as set forth in claim 14 wherein the respective radiation limiting device is a fluorescer device and the X-ray generating means is positioned to direct a beam of X-radiation onto a portion of the fluorescer device adjacent the selected sample.
 16. An energy dispersive X-ray analyzer apparatus including: an evacuable enclosure comprising a hollow housing having a convergent pair of sloped walls hermetically attached to one another in an apex joint located approximately over a test position within the housing; a sample selecting means comprising turntable means for supporting with the housing a circular array of arcuately spaced samples, one being located in the test position, and means for rotating a selected sample of the array into the test position; X-radiation selecting means comprising apertured disc means for supporting within the housing a circular array of arcuately spaced radiation limiting devices including fluorescer devices one being aligned with the test position, and means for rotating a selected radiation limiting device into alignment with the selected sample; first X-ray generating means hermetically mounted on one of the sloped walls as a defining part of the enclosure, and disposed adjacent the apex joint to direct a beam of X-radiation through the selected radiation limiting device and onto the selected sample; X-radiation detecting means hermetically mounted on the other one of the sloped walls as a defining part of the enclosure and disposed adjacent the apex joint to receive X-rays emitted from the selected sample; and second X-ray generating means hermetically mounted as a defining part of the enclosure or a wall opposite the first X-ray generating means and disposed to direct a beam of X-radiation onto a portion of the selected radiation limiting device adjacent the selected sample. 